Optoelectronic Characterization of Chemical Bath Deposited Cd_xCo_1-xS Thin Film

Abstract

Cadmium Cobalt Sulphide (Cd_xCo_1-xS) thin film was deposited on microscopic glass substrate using chemical bath deposition technique at room temperature from aqueous solutions of Cadmium Chloride, Cobalt Chloride and Thiourea in which ammonium solution was used as complexing agents. The optical properties were characterized using the absorbance and transmission measurement from Unico UV-2102 PC spectrophotometer, at normal incidence of light in the wavelength range of 200 - 1000 nm. We report the deposition and optimization of the growth parameter with respect to time which showed that the band gap energy and the composition verified from the extended Vegard’s law are highly dependent on deposition time. The average transmittance of the film in VIS-NIR region ranges between 30% and 78% with absorbance range of 0.15 - 0.47 within the same wavelength range. The film was also observed to exhibit poor reflectance (11 < R% < 20) which declined albeit exponential within the entire studied wavelength range. From absorbance and transmittance spectra, the band gap energy determined for the film deposited at various time: 19 h, 21 h and 24 h are 2.25 eV, 2.17 eV and 2.05 eV respectively, in that order. The composition of the ternary system for 19 h; 21 h, and 24 h were found to be (<i>x</i> = 0.75; 0.83 and 0.94), respectively. Other optical and dielectric properties of the films were also characterized. Based on the exhibited properties of the film, it can be concluded that it is a promising material for selective coatings for solar cells; effective coatings for poultry houses; use as antireflective coating materials, and for fabrication of optoelectronic devices.